In prior art hydraulic systems in which hydraulic actuators are used, for example, for support or lifting systems, hydraulic accumulators as spring or damper elements are hydraulically coupled to the actuator for cushioning or attenuating the movements of components moved by the hydraulic actuator. In some operating situations of such systems, however, an uncushioned, rigid dynamic connection between the actuator and the device actuated thereby is necessary, for example, for a hydraulically actuated boom intended to form a rigid support element, or for a tool to be controlled vibration-free when in use. In view of these requirements, the connection between the pertinent actuator and the hydraulic accumulator must be blocked.
In operation with the spring system blocked, the effective pressure in the hydraulic actuator changes according to the performance to be delivered by it. If at this point the system is transferred from the state of the blocked spring system back into the state with the hydraulic accumulator connected, a difference in the effective pressure between the hydraulic accumulator and the actuator leads to uncontrolled motion at the actuator. This uncontrolled motion poses a hazard to the system and a safety risk for system operators.